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February 9, 2009- Antiretroviral drug therapy in an HIV-positive man or women can alone help prevent the transmission of HIV to an uninfected partner, regardless of counseling, the patient’s use of condoms or other safe-sex practices, AIDS experts at Johns Hopkins report.

In a study among 205 so-called discordant couples in Uganda, in which only one member of each heterosexual pair was infected with HIV, researchers found that not a single case of transmission from one partner to the other occurred when the infected man or women was taking potent anti-HIV medications to keep the disease in check.

By contrast, 34 men and women became infected among the 185 remaining couples in which neither partner was taking antiretroviral therapy. The study group pairs consisted of 126 HIV-positive men and 79 HIV-positive women.

The experts caution that drug therapy should not be considered a fail-safe strategy in such couples and that condom use and safe-sex practices are still vitally important. But the results, they say, show that the drugs significantly help lower the risk of transmission.

According to lead study investigator and infectious diseases specialist Steven Reynolds, M.D., M.P.H., the study results show that antiretroviral therapy not only “treats the HIV-infected member of a discordant couple,” but also plays some role in preventing the virus from spreading.

However, he cautions that its preventive role is limited because of the advanced stage of disease in those being treated in his study group. In Uganda, as in most countries, infected people usually do not qualify for government-funded antiretroviral therapies until the disease has reached an advanced stage, with a CD4 immune system cell count of 200 or less.

Reynolds, an assistant professor at the Johns Hopkins University School of Medicine and a staff clinician at the U.S. National Institute for Allergy and Infectious Diseases, says study results showed that HIV transmission in the treated couples was prevented despite the failure of counseling to halt unsafe sex practices, such as extramarital sex or failure to use condoms.

Participants in the study, conducted jointly by Johns Hopkins and Rakai Health Sciences Program researchers between 2004 and 2007, came from the Rakai cohort, a population of 12,000 people in Uganda who are being monitored to determine how HIV spreads throughout the country. The researchers based their findings on extensive interviews with each participant and an annual check-up during which blood tests were conducted.